Abstract: A unitary intravascular defibrillating catheter includes distal and proximal spring electrodes, displaced to such distance from one another that defibrillating shock is effected through a field including the interventricular septum and left ventricular free wall. In one embodiment of this catheter, the proximal electrode is placed in the region of the subclavian vein. Alternatively, it may be placed in the region of the third through seventh intercostal space. A unitary catheter is also described which includes an intermediate electrode, placed between distal and proximal electrodes. Selection of placement of electrodes either in the superior vena cava or in the region of the subclavian vein is medically indicated by physiological conditions of the individual patient. The cardioversion system further includes a unipolar or bipolar sensing circuit with at least one sensing electrode, and a cardioversion/defibrillation circuit with either two or three spaced apart spring electrodes.

Abstract: A method and apparatus for delivering an adaptive n-phasic waveform to the heart in either a fixed-tilt delivery mode or a fixed-duration delivery mode. A first phase of a first polarity is delivered to the heart. The first phase is set to terminate upon decaying to a preset level. If the first phase does not decay to the preset level within a predetermined maximum period of time, the first phase is terminated and the subsequent phases are delivered in a fixed-duration delivery mode. Because the first phase did not decay fast enough, it is determined that the patient has a relatively high system impedance. Therefore, subsequent phases will be delivered to the patient in a fixed-duration mode to insure the defibrillation is reversed. Otherwise, if the first phase decays to the preset level in less than the maximum predetermined period of time, it is determined that the patient has a relatively low system impedance and subsequent phases should be delivered in a fixed-tilt mode.

Abstract: Implantable electrodes for defibrillation are formed of pluralities of electrode segments. Each of the segments is relatively long and narrow. The electrode segments can be parallel and spaced apart from one another a distance at least ten times the nominal width, with one end of each segment mounted to a transverse distal portion of an electrically conductive lead coupling the electrode to a defibrillation pulse generator. Alternatively, segments can branch or radiate outwardly from a common junction. In yet another arrangement, electrode segments are portions of a single conductive path at the distal end of a lead from a pulse generator, arranged in either a spiral configuration or a serpentine configuration which can align electrode segments side by side, parallel and spaced apart.

Abstract: Implantable electrodes for defibrillation are formed of pluralities of electrode segments. Each of the segments is relatively long and narrow. The electrode segments can be parallel and spaced apart from one another a distance at least ten times the nominal width, with one end of each segment mounted to a transverse distal portion of an electrically conductive lead coupling the electrode to a defibrillation pulse generator. Alternatively, segments can branch or radiate outwardly from a common junction. In yet another arrangement, electrode segments are portions of a single conductive path at the distal end of a lead from a pulse generator, arranged in either a spiral configuration or a serpentine configuration which can align electrode segments side by side, parallel and spaced apart.

Abstract: A defibrillation electrode for implantation in the region of the heart and for connection to a defibrillation system. The electrode comprises multiple independent conductive segments spaced apart for defining a discharge surface of the electrode. In one embodiment, the electrode comprises a plurality of concentric conductive rings electrically connected together. To smooth the current distribution, the interface impedance of the inner conductive segments is made lower than that of the outer conductive segments. In one embodiment, the impedance is determined by the choice of the conductive material. In another embodiment, the impedance is determined by texturing the surface of the conductive segments. In yet another embodiment, the impedance is determined by the ratio of conductive edges to surface of the conductive segment. The discharge surface region can also take the form of a portion of a cardiac catheter.

Abstract: A defibrillation electrode for implantation in the region of the heart and for connection to a defibrillation system. The electrode comprises multiple independent conductive segments spaced apart for defining a discharge surface of the electrode. In one embodiment, the electrode comprises a plurality of concentric conductive rings electrically connected together. To smooth the current distribution, the interface impedance of the inner conductive segments is made lower than that of the outer conductive segments. In one embodiment, the impedance is determined by the choice of the conductive material. In another embodiment, the impedance is determined by texturing the surface of the conductive segments. In yet another embodiment, the impedance is determined by the ratio of conductive edges to surface of the conductive segment. The discharge surface region can also take the form of a portion of a cardiac catheter.

Abstract: A unitary intravascular defibrillating catheter includes distal and proximal spring electrodes, displaced to such distance from one another that defibrillating shock is effected through a field including the interventricular septum and left ventricular free wall. In one embodiment of this catheter, the proximal electrode is placed in the region of the subclavian vein. Alternatively, it may be placed in the region of the third through seventh intercostal space. A unitary catheter is also described which includes an intermediate electrode, placed between distal and proximal electrodes. Selection of placement of electrodes either in the superior vena cava or in the region of the subclavian vein is medically indicated by physiological conditions of the individual patient.The cardioversion system further includes a unipolar or bipolar sensing circuit with at least one sensing electrode, and a cardioversion/defibrillation circuit with either two or three spaced apart spring electrodes.

Abstract: Implantable electrodes for defibrillation are formed of pluralities of electrode segments. Each of the segments is relatively long and narrow. The electrode segments can be parallel and spaced apart from one another a distance at least ten times the nominal width, with one end of each segment mounted to a transverse distal portion of an electrically conductive lead coupling the electrode to a defibrillation pulse generator. Alternatively, segments can branch or radiate outwardly from a common junction. In yet another arrangement, electrode segments are portions of a single conductive path at the distal end of a lead from a pulse generator, arranged in either a spiral configuration or a serpentine configuration which can align electrode segments side by side, parallel and spaced apart.

Abstract: Implantable electrodes for defibrillation are formed of pluralities of electrode segments. Each of the segments is relatively long and narrow. The electrode segments can be parallel and spaced apart from one another a distance at least ten times the nominal width, with one end of each segment mounted to a transverse distal portion of an electrically conductive lead coupling the electrode to a defibrillation pulse generator. Alternatively, segments can branch or radiate outwardly from a common junction. In yet another arrangement, electrode segments are portions of a single conductive path at the distal end of a lead from a pulse generator, arranged in either a spiral configuration or a serpentine configuration which can align electrode segments side by side, parallel and spaced apart.

Abstract: A defibrillation electrode for implantation in the region of the heart and for connection to a defibrillation system. The electrode comprises multiple independent conductive segments spaced apart for defining a discharge surface of the electrode. In one embodiment, the electrode comprises a plurality of concentric conductive rings electrically connected together. To smooth the current distribution, the interface impedance of the inner conductive segments is made lower than that of the outer conductive segments. In one embodiment, the impedance is determined by the choice of the conductive material. In another embodiment, the impedance is determined by texturing the surface of the conductive segments. In yet another embodiment, the impedance is determined by the ratio of conductive edges to surface of the conductive segment. The discharge surface region can also take the form of a portion of a cardiac catheter.

Abstract: A cardioversion/defibrillation system employing a dual biphasic and multi-electrode discharge technique for effectively defibrillating the heart by creating a voltage gradient throughout substantially all of the heart which is above a critical voltage gradient while delivering a minimum energy shock. Effective cardioversion/defibrillation is accomplished by delivering two shocks to the heart. The first shock is at an energy level lower than that typically necessary to cardiovert/defibrillate the heart alone, and is applied between a first pair of cardioversion/defibrillation electrodes. The second shock is at an energy less than the first shock and is applied between a second pair of electrodes to shock the area of the myocardium provided with an inadequate voltage gradient from the first shock. The voltage gradient in the low gradient areas is boosted above the minimum gradient necessary to defibrillate.

Abstract: A system for determining the defibrillation threshold energy of a defibrillation lead arrangement by shocking the heart during the T wave of the ECG at decreasing energy levels until the heart is placed in fibrillation. The lowest energy level tested which fails to place the heart in fibrillation correlates to the defibrillation threshold energy of the lead arrangement.

Abstract: A cardioversion system includes a bipolar sensing circuit with two sensing electrodes, and a cardioversion circuit with two spaced apart spring electrodes. The sensing electrodes are spaced apart from one another but kept sufficiently close to one another for isolated, localized R-wave sensing. The sensing electrodes further are positioned remotely of the cardioversion electrodes, to avoid post-shock abnormalities which otherwise would interfere with a timely R-wave sensing, to substantially prevent the discharge of an unnecessary cardioversion pulse after return of the heart to normal cardiac rhythm. One preferred version of the system is a unitary catheter including a distal tip electrode and ring electrode as the sensing electrodes, and to substantially larger, more proximal spring electrodes for defibrillation. Alternatively, the defibrillation electrodes and the sensing electrodes can be provided on two separate catheters.

Abstract: An apparatus for stimulating and sensing evoked response to stimulus in the heart. First and second electrodes are in electrical contact with the heart, a third indifferent electrode is also in electrical contact with the heart. A pacemaker provides stimulus signals through the electrodes in the stimulating mode of operation. The first and second electrodes are switched through switching apparatus wherein in the first mode the first and second electrodes are maintained at equal electrical potentials, and in a second, sensing mode, the switch operates between the first and second electrodes so as to allow the first and second electrodes to act as bipolar sensing leads. Evoked response is sensed by a differential amplifier having a first differential input connected to the first electrode and a second differential input connected to the second electrode. The differential amplifier provides a differential signal which is proportional to the evoked cardiac response.